Rapid developments in the ability to perceive and understand others' emotions are made during infancy. Within a few short months, infants move from an initial, limited ability to detect individual components that make up an expression to discriminating and categorizing emotional expressions that belong together. Development of an awareness and understanding of what people think, feel, and do is critical to children's effective functioning in their social worlds. The proposed research will examine infants' developing proficiencies in the perception of other persons' emotional expressions. One set of experiments will ask whether infants discriminate emotional expressions at a young age (3-4 months) when these expressions are portrayed in familiar contexts and by familiar persons. Several experiments will rely on an intermodal matching procedure to determine whether infants recognize a variety of emotional expressions portrayed by either their fathers or mothers or strangers. Infants will also be tested for their ability to detect invariant information across parental expressions of emotion. A second set of studies will investigate the role of acoustic and visual information in older infants (7 months) discrimination of emotional expressions. Infants will be habituated to happy and sad facial/vocal expressions and tested for their discrimination of the auditory and visual components of these expressions.